JPH01240887A - Radiation detector and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a radiation detector easy to mount with limited crosstalk between adjacent channels, by providing a separator plate between a plurality of scintillators and amorphous photodiodes made on a support body. CONSTITUTION:A scintillator element 1 is a rectangular parallelopiped, disposed in proximity to other scintillators and amorphous photodiodes (PD) 2 are formed directly on a surface opposite to an X rays incident surface with the largest area while a support body 3 is put tight on the X rays incident surface to support the scintillator elements. A separator plate 6 is between the scintillator elements to remove crosstalk between the elements. With such an arrangement, as the PD is exposed, sensitivity distribution of the elements is measured for each radiation element to trim the PD by a laser trimming method thereby enabling adjustment to make the sensitivity distribution uniform.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radiation detection element used in an X-ray CT apparatus, and in particular, the present invention relates to a radiation detection element used in an X-ray CT apparatus, and in particular has a detection sensitivity variation between elements and a radiation incident position within the element, which has little sensitivity variation. 6. Concerning a Radiation Detection Element with Less Crosstalk with Adjacent Channels, High S/N, and Easy Mounting [Prior Art] A typical solid-state detection element for CT is a combination of a scintillator and a PD. An example of its implementation is, for example, Japanese Patent Laid-Open No. 58-118977.

Further, due to recent advances in applied research on amorphous materials, amorphous silicon PDs can also be used as the PDs. Examples of this include JP-A-62-71881 and JP-A-6
There is 2-43585.

[Problem to be solved by the invention]

The above conventional technology using amorphous silicon has problems because it does not take into account the following points.

(1) No consideration is given to the efficient mounting of a large number of elements with high precision, and misalignment between adjacent elements often occurs. As a result, if this detection is used in a CT device, CT
Both image artifacts may occur or image quality may deteriorate.

(2) No consideration is given to crosstalk between adjacent elements, resulting in artifacts in both CT images, reduction in image contrast resolution, and deterioration in spatial resolution.

(3) Since the mounting process is complicated and requires high positional accuracy between adjacent elements, mounting requires highly skilled techniques, significantly increases manufacturing costs, and has a poor yield.

On the other hand, in the conventional mounting method of a solid-state detection element in which a crystalline silicon photodiode is bonded to a scintillator, the support plate is used only as a support plate for the crystalline PD or simply to fix the scintillator element, so an amorphous PD is used. Even if an attempt was made to use the integrated solid-state detector as is, it did not contribute to improving the performance of the integrated detector as a whole or simplifying the mounting process.

The object of the present invention is an amorphous PD, a scintillator.

By optimizing the positional relationship and shape of the support and the support body, the advantages as an integrated detector can be fully demonstrated, and the above-mentioned problems can be solved, namely:
The object of the present invention is to provide a radiation detector that is high-performance, low-cost, and easy to mount, without misalignment between adjacent elements, crosstalk between adjacent elements, or complicated mounting process.

[Means for solving problem 8] The above purpose is to provide at least a plurality of scintillator elements, a plurality of P
D. A radiation detector consisting of one or more supports, in which the plurality of scintillator elements are arranged one-dimensionally or two-dimensionally orthogonally to the incident input plane of the radiation to be detected, at least as F D. Using an amorphous PD, the amorphous P
D is directly formed on at least one scintillator surface having a maximum area among the scintillator surfaces excluding the surfaces where the scintillator element groups are adjacent to each other, and the amorphous PD forming surface of the scintillator surface having the maximum area is formed. Alternatively, the scintillator surface having the largest area other than the surface is tightly fixed to the support, and wiring for detecting the output signal of the amorphous PD is provided on the surface of the support that is in contact with the scintillator or on a surface parallel to the surface. This is achieved by electrically connecting the wiring and the amorphous PD and disposing a light or radiation shielding layer between the plurality of scintillators.

[Effect]

(1) Since the support body supporting the scintillator elements is supported in contact with the scintillator surface excluding the surfaces where the scintillator element groups contact each other, after attaching the large area scintillator to the support body, grooves are cut in the scintillator, A plurality of scintillator element groups can be formed. Therefore, the positional accuracy between adjacent elements is determined only by cutting, and the positional accuracy is improved. Furthermore, the mounting process can be simplified.

In addition, since the surface having the largest area of the scintillator element is used as the contact support surface between the scintillator and the support, the mechanical strength of the scintillator in the cutting process is increased, and cracks, cracks, etc. of the scintillator during cutting can be prevented. will improve.

(2) Since the amorphous photodiode is directly formed on the surface of the scintillator having the largest area, the geometric efficiency of detecting light from the scintillator is extremely high, and the S/N ratio is improved. Furthermore, since the PD is directly formed on the scintillator surface, there is no need for a step of laminating the scintillator PD, unlike in the case of crystalline PD, and the mounting can be significantly simplified.

(3) Since the signal extraction surface of the amorphous PD and the signal extraction wiring of the support plate are formed on mutually parallel surfaces, connection is easy and the mounting process is simplified.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1(a), the scintillator element 1 is a rectangular parallelepiped, and its size is, for example, 30 + nm x 1, 2 m.
X 1 , Omm. This scintillator element is adjacent to other scintillator elements in a plane of 30 mm x 1.2+m. The length of the scintillator element in the X-ray incident direction is determined by the xlIA absorption rate, and the length of the element array in the direction is determined by the required spatial resolution of the CT apparatus. The length in the direction perpendicular to the element array is defined by the slice thickness during CT imaging.

This scintillator element has the largest area among the surfaces excluding the adjacent surfaces of the scintillator element group (30nnX
1. Amorphous PD2 is directly formed on the surface (having an area of 0 mm). For amorphous PD, S/N is determined by direct X-ray radiation.
It is formed on the surface opposite to the X-ray incident surface in order to avoid a decrease in X-rays and X-ray deterioration.

As a result, the amount of X-rays directly incident on the PD is 1/10~
It decreases to 1/100. Further, a support 3 for supporting a group of scintillator elements is in close contact with a surface (X-ray incidence surface; having the same area) opposite to this surface. Here, the support 3 is a material or shape having low X-ray absorption, such as a thin plate (for example, thickness inn to 3 mm) of alumina, glass, epoxy, or other ceramic material. The output signal of the PD 2 is taken out by the wiring 4 formed on the support body by a connecting line 52 such as an AQ or Au wire. This wiring 4
For example, the wiring may be Au wiring or AQ wiring printed on three surfaces of the ceramic support. Furthermore, separator plates 6 are present between the scintillator elements to eliminate crosstalk between the elements.

Next, the amorphous PD portion will be described in detail using FIG. 1(b). As the amorphous PD 2, a PIN structure PD made of, for example, amorphous 5i (abbreviated as a-8i) is used.

Its structure is a transparent protective film formed directly on the scintillator.7. Transparent electrode 8 + P type a-8i (amorphous silicon) layer 9. i-type a-Si layer 10. n-type a-3i layer 11. It consists of an electrode 12. The signal is transmitted through transparent electrode 8. It is obtained as a current flowing between the electrodes 12. A separator plate 6 for optically or radiologically separating each scintillator element is inserted and fixed in the separator plate insertion groove 13.

According to this structure, since the PD is exposed, as shown in FIG.
) The sensitivity distribution of the elements (201 to 203) formed as shown in FIG. It is possible to adjust the sensitivity distribution so that it becomes uniform as shown in (d) of the same figure by cutting as shown in c).

In this example, since the amorphous PD portion is exposed when the detector is mounted, the sensitivity variations between detector elements and the sensitivity variations within the element are measured when the detector is mounted, and based on the measurement results, The PD shape can be easily changed to eliminate this variation. In other words, the sensitivity can be finely adjusted after mounting. As a result, an extremely ideal CT detector is obtained, completely free from both of the above-mentioned variations.

Next, an example of the manufacturing method of the above-mentioned example will be described with reference to FIG.

(a) One surface of a scintillator having a size equivalent to 2, eg, 8 elements, such as a GdzOzS ceramic scintillator, is mirror-polished, and a transparent protective film 71, eg, 5 iOz, is formed on this surface. Next, the transparent electrode 82, for example, 5nO
0-order p-type a-8i film 97 forming a x, ITO, or Snow/ITo2ff film, for example, with a film thickness of 0.01 pm
a-SiC:H film, i-type a-8i film 10. For example, an a-3i:H film with a film thickness of 1.5 μm, an n-type a St film 11
2. For example, a PC-8i:H film having a thickness of 0.03 μm is sequentially formed. Next, an electrode 122, for example, an AI2 vapor deposited film, is formed using an electrode forming mask. After forming the electrode, the amorphous film other than the electrode forming area is removed by plasma etching.

(b) The scintillator/amorphous PD is placed on a support 3°, such as an alumina ceramic substrate, a machinable ceramic substrate, a glass epoxy substrate, etc., on which Au printed wiring is applied, for example.

For example, it is firmly bonded using an epoxy adhesive.

Strongly adheres to the support over a large area. As a result of strong adhesion to the support over a large area, the mechanical strength of the scintillator is significantly improved.

(c) The scintillator is cut along the divisions of the amorphous PD element formed on the scintillator to form grooves 6 for inserting separator plates. Grooves can be formed using, for example, a diamond cutter.
Using a wire saw, the groove width is set slightly larger, for example, 10 to 20 μm, than the separator plate to be inserted. Each groove is formed to completely cut the scintillator and shave the support plate to a certain extent, for example 30 μm-100 μm.

In this step, since the mechanical strength of the scintillator has already been increased by the support, bubble control, cracking, etc. of the scintillator will not occur. A separator plate is inserted and fixed into this groove. The separator plate may be a molybdenum plate or the like on which a metal reflective film, such as an AQ vapor deposited film, is formed. For example, an epoxy adhesive is used to fix the separator plate.

An example of the state after adhesion is shown in FIG. If a light-shielding material is used as the adhesive material 14, there will be no leakage of scintillation light to adjacent channels, and crosstalk can be prevented. The adhesive material 14 is not only used for fixing the separator plate, but may be formed to cover the entire PD.

In this case, there is no leakage of light from the outside, and the S/N of the detection signal can be improved.

Further, light-reflecting powder may be mixed into the adhesive 14. This effect is due to the fact that P[i] of the light from the scintillator
Since the light leaking from the non-forming portion can be returned into the scintillator by the reflective material and detected by the PD, the photodetection signal increases and the S/N ratio improves.

Next, another embodiment of the present invention will be described with reference to FIG.

The present invention is the first. The difference from the third embodiment lies in that a light reflecting layer 15 is formed on the surface of the scintillator element 1 on the support adhesion side. The light reflecting layer 15 is, for example, an AQ vapor deposited film or an AQ vapor deposited film.
A U film, Ag film, Cr film, etc. may be used. Making the scintillator surface a mirror surface improves the light reflectance. When using a ceramic scintillator, it may not become completely flat even after mirror polishing, so in this case, a transparent film such as 5i02. Sn○2. SiN4. The light reflection efficiency can be improved by forming PIQ or the like on the scintillator surface to form a flat surface and forming a light reflection film thereon.

In this embodiment, the light emitted from the upper surface of the scintillator is also reflected by the light reflecting layer and enters the photodiode surface to become a signal component, so that the photosensitivity is significantly improved.

The structure described in this embodiment is also employed in the embodiments shown in FIGS. 6 and 8, and its effects are extremely large.

Next, another embodiment of the present invention will be described using FIG. 6. The feature of this embodiment is that a light reflecting layer is provided between adjacent PDs. In FIG. 6(a), after the transparent protective film 79 is formed, for example, Si○2, the light coating film 19 is formed, for example, λQ, Cr, Au.
, Ag, etc. are patterned by, for example, a vapor deposition method. Thereafter, transparent electrodes 82 such as 5nOz, ITO, etc. are formed, and the a-8i films 9, 10, 11 . A metal electrode 12 is formed.

Let it be PD2. The transparent electrode 8 may be formed in a pattern as shown in the figure, or may be formed over the entire surface.

In this example, since a light reflecting film is arranged on the part of the PD forming surface where no PD is formed, there is no leakage of scintillator light from this surface, and the amount of detected light increases, so that the signal S
/N increases. Furthermore, since light can be prevented from entering adjacent elements, crosstalk is reduced.

FIG. 6(b) shows an example in which the light reflecting layer 19 is formed after the transparent electrode 8a is formed.

FIG. 6(c) shows an example in which after forming the PD 2, the entire surface is covered with an insulating protective film 201 such as 5iOz, PTQ, etc., and then a light reflecting film 19 is formed. In addition to the function of reflecting scintillator light,
It functions to prevent external light from leaking into the PD2.

FIG. 6(d) is in the embodiment of FIG. 6(, l).

A case is shown in which a light shielding material layer 21 is provided as the final step. This light shielding material serves to prevent light from entering the PD 2 from the outside and to increase mechanical strength.

In the embodiments (a) to (d) above, a transparent film 18 is provided on the scintillator surface as in the embodiment explained using FIG.
A light reflecting film 179, for example, an AQ vapor-deposited film is formed through, for example, 5iOz or PIQ, and is designed to efficiently reflect light on the upper surface of the scintillator and increase the amount of light detected by the photodiode.

Further, the separator plate can be easily formed by the same method as the embodiment described using FIG. 3.

Next, a method of bonding the support and the scintillator block will be explained using FIG. In the figure, X-rays enter from the support 3 side.

The support 3 is made of ceramic (alumina, machinable ceramic, etc.), and has a thickness of 0.5 to 3 m. It is desirable that the thickness be uniform at least in the area range into which X-rays are incident.

On the surface of the support, there is a signal output line 4, for example Au.

It is formed with AQ printed wiring. The printed wiring has a thickness of, for example, 0.1 to 1 μm and a reduced width of 200 to 500 μm.

The scintillator is, for example, Gd2O2S: PN, Ce, F.
A ceramic scintillator, for example, with a thickness of 1 to 2 w1
1, a-8iPD is formed on the scintillator surface. The PD area is, for example, 1 + na x 25 m, and the element spacing is, for example, 150 μm to 300 μm.

The element and the wiring portion on the support are electrically coupled by wire bonding of, for example, Au or AQ. The wire diameter may be, for example, 25 μφ. Further, the area of the bonding pad may be, for example, 100 μm to 500 μm.

The scintillator and the support are bonded together by an adhesive 9, such as an epoxy adhesive. Adhesive thickness is, for example, 5 to 30μ
It is m.

After bonding, groove 1 is placed parallel to the longitudinal direction of the PD element with high positional accuracy.
form 3. Also, at the end, the scintillator and support are cut off with high precision. In this way, an element block with high positional accuracy can be easily formed.

After the grooves are formed, a separator plate is inserted and fixed into the grooves.

Finally, cover the entire element with a photosensitive resin.

Arrange the required number of element blocks in a flat or curved manner and
Figure 8 illustrates the shape of the support and the PD multiplier signal output section.

In FIG. 8(a), the support is very large only at the xa incident portion, and the support reduces Xa absorption.

In the PD section double signal extraction section, a metal film such as AQ, NiCr, etc. is formed on the transparent electrode on the transparent electrode side.

The difference between FIG. 8(b) and FIG. 8(a) is that the scintillator joining portion of the support is slightly higher than the signal output line forming portion. This thickness is, for example, 30 μm
It is about -200 μm.

According to this structure, since there is no need to cut the ground electrode etc. when forming the separator plate insertion groove 13, the degree of freedom in printed wiring on the support body is increased.

In other words, the size of the support step of this structure.

If the value is (grooving depth into the support body) + (wiring pattern thickness) or more, the effects described in this embodiment can be obtained.

FIG. 9 shows another example of the shape of the support.

This embodiment has a feature that bonding can be easily performed because the PD section and the signal output wiring on the surface of the support are located on a plane between one side and the other.

In the above embodiments, the height and length of the separator plate need only be larger than the thickness and length of the scintillator, and there is no need to make the accuracy of one dimension extremely strict, so that the separator plate can be manufactured easily.

FIG. 10 shows an example of the implementation of the CT table device of the detector. The support body is attached to the CT apparatus detector section housing with high positional accuracy using attachment screws. The scintillator and photodiode sections are completely isolated from the outside by the casing, and are protected from heat and light leaking from the outside. The housing is made of AQ or ceramic, for example. If necessary, a film may be installed on the contact surface between the body and the support 5 and the X-ray incident surface of the support to remove moisture and light leakage 6 [Effects of the Invention] The present invention According to the method, an amorphous PD is directly formed on a scintillator, and amorphous PD is formed by wiring arranged on a scintillator support.
It is possible to take out the output signal of D, and it is easy to optimize the relationship between the support, scintillator, and amorphous PD, so it is possible to achieve high S/N, high positional accuracy, and easy-to-implement radiation. This has the effect of providing a detector.

[Brief explanation of the drawing]

FIG. 1 is a perspective view and a cross-sectional view of a main part of a radiation detector showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of a radiation detector according to an embodiment of the present invention, and a detection sensitivity characteristic diagram, FIG. 3 is a cross-sectional view showing the manufacturing process of a radiation detector according to an embodiment of the present invention, and FIGS. 4, 5, 6, and 8 are cross-sectional views of radiation detectors according to embodiments of the present invention. Figure 7 shows the bonded portion between the scintillator and the support according to the embodiment of the present invention) T1 side view and side sectional view, Figure 9 is a cross-sectional view showing the shape of the scintillator support, and Figure 10 is the book. A cross-sectional view of the main parts of an X-ray CT apparatus showing the implementation mode of the detector according to the embodiment of the invention.
Wooden KZ diagram 3 diagram

Claims (1)

[Claims] 1. Consisting of at least a plurality of scintillator elements, a plurality of photodiodes (abbreviated as PD), and one or more supports, the plurality of scintillator elements being perpendicular to the incident direction of the radioactivity to be detected. In a radioactive detector arranged one-dimensionally or two-dimensionally, at least an amorphous PD is used as the PD, and the amorphous PD is arranged on a scintillator surface excluding the surface where the scintillator element groups are adjacent to each other. Formed directly on at least one scintillator surface having the largest area among them, and bringing the amorphous PD forming surface of the scintillator surface having the largest area or the scintillator surface having the largest area other than this surface into close contact with the support. Wiring for detecting the output signal of the amorphous PD is provided on the surface of the fixed support that is in contact with the scintillator, or on a surface parallel to the surface, the wiring is electrically connected to the amorphous PD, and A radiation detector characterized in that a light or radiation shielding layer is arranged between the plurality of scintillators. 2. When manufacturing the radioactive detector according to claim 1, the light or radiation shielding layer forming step is performed at least in the step of forming an amorphous PD of the scintillator, the step of wiring on the support, and the step of forming the scintillator. A method for manufacturing a radiation detector, characterized in that the method is carried out after the step of laminating a support. 3. The radiation detector according to claim 1, wherein the amorphous PD forming surface of the scintillator is a surface facing the X-ray incident surface. 4. The radiation detector according to claim 3, wherein the support is adhered to the X-ray incident surface of the scintillator, and the support is made of a material or shape having low X-ray absorption. 5. A radiation detector according to claim 1, wherein the support and the wiring arranged on the support are ceramic plates and printed wiring, respectively. 6. The radiation detector according to claim 1, characterized in that the electrical connection between the amorphous PD and the wiring on the support is a wire bonding method. 7. A radiation detector according to claim 1, characterized in that a light reflecting film is formed on at least one surface of the scintillator other than the surface on which the amorphous PD is formed, with a transparent protective layer interposed therebetween. 8. A radiation detector according to claim 7, wherein the light reflecting film is made of a metal thin film. 9. A radiation detector according to claim 1, characterized in that a light reflecting film is formed on at least a portion of the amorphous PD-forming surface of the scintillator where the amorphous photoconductive film is not formed. 10. A radiation detector according to claim 9, wherein the light reflecting film is a metal thin film. 11. In claim 1, of the scintillator adhesive surface of the support, the scintillator adhesive part is slightly convex than other parts, and printed wiring for signal extraction is provided on the other parts. A radiation detector featuring: 12. The radiation detector according to claim 1, wherein the scintillator and the amorphous PD section are optically and thermally isolated from the outside.